The syntheses of new geometric isomers of vitamin A, A2 and carotenoids will be continued. Some of the specific target molecules during the next budget year are: vitamin A, A2 isomers containing the 7,11-dicis geometry and beta-carotene isomers containing the 7-cis and 7,7'-dicis geometry. Stereoselective synthesis of the known 7-cis and 7,13-dicis isomers will be attempted. These studies will be conducted in parallel with a cancer contract study of cancer preventive properties of vitamin A isomers. A preparative hplc unit will become available to assist the synthetic effort. A more concentrated effort in studying visual pigment analogs will be conducted during the coming year. The study will include 7-cis rhodopsin and porphyropsin analogs, and further examination of properties of the fluorinated analogs. We have prepared most of the desired retinal analogs. So, it is quite appropriate to have the addition of a post-doctoral during the last year of this research program to devote his time completely in this direction.